This question already has an answer here:
In Java I can do by using an Iterator
and then using the .remove()
method of the iterator to remove the last element returned by the iterator, like this:
import java.util.*;
public class ConcurrentMod {
public static void main(String[] args) {
List<String> colors = new ArrayList<String>(Arrays.asList("red", "green", "blue", "purple"));
for (Iterator<String> it = colors.iterator(); it.hasNext(); ) {
String color = it.next();
System.out.println(color);
if (color.equals("green"))
it.remove();
}
System.out.println("At the end, colors = " + colors);
}
}
/* Outputs:
red
green
blue
purple
At the end, colors = [red, blue, purple]
*/
How would I do this in Python? I can't modify the list while I iterate over it in a for loop because it causes stuff to be skipped (see here). And there doesn't seem to be an equivalent of the Iterator
interface of Java.
Iterate over a copy of the list:
for c in colors[:]:
if c == 'green':
colors.remove(c)
Best approach in Python is to make a new list, ideally in a listcomp, setting it as the [:]
of the old one, e.g.:
colors[:] = [c for c in colors if c != 'green']
NOT colors =
as some answers may suggest -- that only rebinds the name and will eventually leave some references to the old "body" dangling; colors[:] =
is MUCH better on all counts;-).
You could use filter function:
>>> colors=['red', 'green', 'blue', 'purple']
>>> filter(lambda color: color != 'green', colors)
['red', 'blue', 'purple']
>>>
or you also can do like this
>>> colors = ['red', 'green', 'blue', 'purple']
>>> if colors.__contains__('green'):
... colors.remove('green')
来源:https://stackoverflow.com/questions/1352885/remove-elements-as-you-traverse-a-list-in-python